package com.linyaonan.leetcode.sword_to_offer._25;

class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        // 特殊情况
        if (l1 == null) {
            return l2;
        }
        if (l2 == null) {
            return l1;
        }

        ListNode head = new ListNode(-1);
        ListNode r = head;

        while (l1 != null && l2 != null) {
            if (l1.val < l2.val) {
                head.next = l1;
                l1 = l1.next;
            } else {
                head.next = l2;
                l2 = l2.next;
            }
            head = head.next;
        }

        if (l1 != null) {
            head.next = l1;
        } else {
            head.next = l2;
        }

        return r.next;
    }
}